The compounds of formula (I) are known to inhibit the synthesis of thromboxane A.sub.2 and have therapeutic effects on ischemic heart diseases (U.S. Pat. No. 4,665,188), but are unknown for their antidiabetic effects.
(E)-3-(4-(1-Imidazolylmethyl)phenyl)propenoic acid hydrochloride is known to inhibit the synthesis of thromboxane A.sub.2. This compound was orally administered to diabetic test animals, however, the effect obtained was not satisfactory for the treatment (Abstract of the 27th Congress of the Japanese Society of Nephrology 196, (1984)).